Btrfs: avoid setting ->d_op twice

Follow those instructions, and you'll trigger a warning in the
beginning of d_set_d_op():

  # mkfs.btrfs /dev/loop3
  # mount /dev/loop3 /mnt
  # btrfs sub create /mnt/sub
  # btrfs sub snap /mnt /mnt/snap
  # touch /mnt/snap/sub
  touch: cannot touch `tmp': Permission denied

__d_alloc() set d_op to sb->s_d_op (btrfs_dentry_operations), and
then simple_lookup() reset it to simple_dentry_operations, which
triggered the warning.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1be31368e881a2c88f2b4ea1f96373bfdaa19786..a682c267576db43f1406ca9da0694b64fa95879e 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4069,7 +4069,7 @@ static struct inode *new_simple_dir(struct super_block *s,
        BTRFS_I(inode)->dummy_inode = 1;
 
        inode->i_ino = BTRFS_EMPTY_SUBVOL_DIR_OBJECTID;
-       inode->i_op = &simple_dir_inode_operations;
+       inode->i_op = &btrfs_dir_ro_inode_operations;
        inode->i_fop = &simple_dir_operations;
        inode->i_mode = S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
@@ -4140,14 +4140,18 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
 static int btrfs_dentry_delete(const struct dentry *dentry)
 {
        struct btrfs_root *root;
+       struct inode *inode = dentry->d_inode;
 
-       if (!dentry->d_inode && !IS_ROOT(dentry))
-               dentry = dentry->d_parent;
+       if (!inode && !IS_ROOT(dentry))
+               inode = dentry->d_parent->d_inode;
 
-       if (dentry->d_inode) {
-               root = BTRFS_I(dentry->d_inode)->root;
+       if (inode) {
+               root = BTRFS_I(inode)->root;
                if (btrfs_root_refs(&root->root_item) == 0)
                        return 1;
+
+               if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
+                       return 1;
        }
        return 0;
 }